There is an established need in the electronics industry to apply layers of flowable coating materials such as spin-on glass to the surface of electronic components. As used herein, "flowable coating materials" includes:
spin-on glass, which is a suspension of glass particulates in a liquid, such as water or a solvent; PA1 polymers such as silicones, polyimides, polyamides, and epoxy; and PA1 melts (melted materials, including metals and plastics).
It is known in the prior art to apply a layer of spin-on glass to a surface of an electronic component by mounting the component on a turntable so that its surface is horizontal and, while rotating the turntable about a vertical axis, dispensing the spin-on glass (e.g., as a dollop of material) onto the surface of the component. The rotation of the turntable (platen) exerts a horizontal rotational force on the spin-on glass which is parallel to the surface of the component. Adhesion and process limitations (e.g., terminating the process) prevents all of the flowable coating material from spinning off of the device. It should be noted that, in this prior art process, the axis of rotation is normal to the surface of the component and is in a vertical direction (pointing at the center of the earth).
Spinning on flowable coating materials in the aforementioned manner is generally effective, unless there are "obstacles" (microstructures) on the surface of the electronic component which either directly or indirectly prevent the glass material from spreading across the surface of the component. Additionally, when a plurality of microstructures are closely spaced on the surface of the component, there will be a tendency for the flowable coating material to "creep" up between adjacent microstructures. The present invention provides method and apparatus for overcoming these limitations.
Reference is made to commonly-owned U.S. patent application Ser. No. 08/152,812 filed Nov. 16, 1993 (now U.S. Pat. No. 4,576,211, issued Dec. 19, 1995), and its counterpart commonly-owned copending "divisional" U.S. patent applications Ser. Nos. 08/457,479 filed Jun. 01, 1995 (status: pending) and 08/570,230 filed Dec. 11, 1995 (status: pending), all by KHANDROS, disclose instances wherein an electronic component has a plurality of free-standing elongate interconnection elements (microstructures, obstacles) mounted to its surface and protruding therefrom. These interconnection elements, may each measure on the order of a few mils in diameter and be spaced only a few mils apart, and may benefit (mechanically) from having a layer of glass material disposed at their bases. Generally, any liquid (flowable) material that is applied to the surface of such a component will tend to creep up (away from the surface of the electronic component) the elongate elements themselves as well as in the spaces between adjacent elongate elements due, primarily, to the forces of surface tension. These forces are of such magnitude that they can substantially prevent spin-on glass material from spreading out in the aforementioned manner along the surface of the electronic component.
What is needed is a technique for applying flowable coating materials such as spin-on glass to the surface of an electronic component that has "obstacles" on its surface, such as the aforementioned component having elongate interconnection elements protruding from its surface. The present invention is not limited to such a component, which is mentioned by way of example only.